One a side note: Have a look at the Modules Environment. I use this every time I have to offer a complex, versioned, self-extensible, concise UNIX environment to dozens or hundreds of users. It's mainly used on large scale multi-user HPC environments. Just using it for one particular variable is certainly over-engineering it, but it does an awesome job once you need more than a few software packages and their environment.

A few have answered saying that /etc/environment is depricated and/or not used in Debian anymore, and this is (as at version 7) false.

The file is actually read by PAM -- specifically, pam_env(8), via a default to the envfile flag. The manpage also states this default under the FILES section.

The wikis quoted (especially the locale one) merely state that locale-based environment variables are now meant to be in /etc/profile. Their statement "(in older versions of Debian, also /etc/environment)" is vague, and is in the context of locales.